It has been conventionally performed to sound plural parts or timbres simultaneously when a user plays a keyboard in an electronic musical instrument. In particular, as a technique (hereinafter referred to as an “ensemble tone generating function”) to distribute notes having plural different tone pitches, which are inputted by simultaneous depressing of plural keys or the like, among plural parts or timbres to sound the notes in the plural parts, there is known an electronic musical instrument which assigns either plural parts or timbres to plural notes inputted by using a keyboard or the like to sound the notes in the respective parts or timbres. For example, in the electronic musical instrument of PTL1, in a unison-two mode, predetermined plural parts (four parts for example), which constitute a composition of musical instruments and to each of which plural different timbres are set, are assigned substantially evenly according to the tone pitch order to respective notes of keys being depressed, thereby allowing that even when the number of notes of keys being depressed changes, the total number of parts to be sounded does not change, and the respective parts are utilized evenly.
Further, in the electronic musical instrument of PTL2, there are provided plural assigners, which assign (correlate) notes of depressed keys to tone generation channels. Each assigner has settings of an assignment priority rule (for example, assignment method: higher-pitch-prior-to-lower-pitch, last-note-prior-to-first-note, lower-note-prior-to-higher-note), a number of notes to be sounded, and timbres (piano A, violin B, or the like). The electronic musical instrument uses plural assigners each of which has suitable settings (for example, an assignment priority rule to be applied, the maximum number of notes of depressed keys able to sound, and timbres to be used in the tone (sound) generation) to enable functions such as dual, split, and so on.
However, in the electronic musical instruments, such as ones disclosed in PTL1 or PTL2, executing an ensemble tone generating function which sounds plural parts or timbres distributed into different keys, in order to obtain an effect of ensemble performance which is done as if respective performers corresponding to the respective parts or timbres play a musical tone independently, musical performance with the number of key depressions (for example, four tones) to a degree equivalent to the number of parts to achieve effective ensemble performance is demanded, which results in quite high difficulty.
On the other hand, there has been also known a technology related to an automatic accompaniment function to which an accompaniment is added automatically to musical performance by a user. For example, in an electronic musical instrument of PTL3, when the automatic accompaniment is on, based on a key depression operation to a key area assigned for automatic accompaniment by a key split point during the automatic accompaniment, a chord is detected and the automatic accompaniment is controlled.